Python function call handler

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Handler types
Synchronous handler
Asynchronous handler
Examples
- HTTP request structure output

A call handler is a method used to process each Python function call. When creating a function version, you should specify an entry point that consists of a file name and a call handler name (such as, main.handler).

Note

At any given time, a single function instance processes only one request. This lets you use global variables without having to provide data integrity control.

When invoking the handler, the runtime passes the following arguments:

Call body (event parameter):
- If the call body is a JSON document, it's converted to dict using the json.loads method.
- If a function was invoked with the integration=raw request string parameter, the HTTP request body is passed to the function as-is (unprocessed).
Invocation context (context parameter).

The context contains the necessary information about the function version. The structure of this object is described in Python function invocation context.

Handler types

A function can use both synchronous and asynchronous request handlers.

Synchronous handler

To have the output returned, use the return statement or raise an exception using the raise statement. A synchronous function must return a result or throw an exception.

Asynchronous handler

A handler can be an async def asynchronous function. In this case you can use the following statements:

return: Returns the function response.
raise: Reports an error to the runtime environment.
await: Tracks the execution of asynchronous function invocations.

Note

The service only supports the asyncio library as a runtime environment for asynchronous functions.

For more information about development using async/await, see the relevant documentation section.

Examples

HTTP request structure output

The following function outputs the request structure and invocation context to both the execution log and function response:

import json


def handler(event, context):
    return {
        'statusCode': 200,
        'body': json.dumps(
            {
                'event': event,
                'context': context,
            },
            default=vars,
        ),
    }

Function invocation example:

curl --data '{"hello": "world"}' -H 'Content-Type: application/json' https://functions.yandexcloud.net/d4eo2faf62**********?param=one

Result:

{
    "context": {
        "aws_request_id": "6e8356f9-489b-4c7b-8ba6-c8cd74f25455",
        "deadline_ms": 1657713543198,
        "function_name": "d4eo2faf62**********",
        "function_version": "d4e3vrugh3**********",
        "invoked_function_arn": "d4eo2faf62**********",
        "log_group_name": "ckgjmanjlh**********",
        "log_stream_name": "d4e3vrugh3**********",
        "memory_limit_in_mb": 128,
        "request_id": "6e8356f9-489b-4c7b-8ba6-c8cd74f25455",
        "token": {
            "access_token": "<IAM token>",
            "expires_in": 42299,
            "token_type": "Bearer"
        }
    },
    "event": {
        "body": "{\"hello\": \"world\"}",
        "headers": {
            "Accept": "*/*",
            "Content-Length": "18",
            "Content-Type": "application/json",
            "Host": "functions.yandexcloud.net",
            "User-Agent": "curl/7.64.1",
            "X-Forwarded-For": "109.252.148.209",
            "X-Real-Remote-Address": "[109.252.148.209]:2816",
            "X-Request-Id": "6e8356f9-489b-4c7b-8ba6-c8cd74f25455",
            "X-Trace-Id": "e9fe9b05-c1aa-4fb8-94d8-a514fd6f3ff7"
        },
        "httpMethod": "POST",
        "isBase64Encoded": false,
        "multiValueHeaders": {
            "Accept": [
                "*/*"
            ],
            "Content-Length": [
                "18"
            ],
            "Content-Type": [
                "application/json"
            ],
            "Host": [
                "functions.yandexcloud.net"
            ],
            "User-Agent": [
                "curl/7.64.1"
            ],
            "X-Forwarded-For": [
                "109.252.148.209"
            ],
            "X-Real-Remote-Address": [
                "[109.252.148.209]:2816"
            ],
            "X-Request-Id": [
                "6e8356f9-489b-4c7b-8ba6-c8cd74f25455"
            ],
            "X-Trace-Id": [
                "e9fe9b05-c1aa-4fb8-94d8-a514fd6f3ff7"
            ]
        },
        "multiValueParams": {},
        "multiValueQueryStringParameters": {
            "param": [
                "one"
            ]
        },
        "params": {},
        "pathParams": {},
        "queryStringParameters": {
            "param": "one"
        },
        "requestContext": {
            "httpMethod": "POST",
            "identity": {
                "sourceIp": "109.252.148.209",
                "userAgent": "curl/7.64.1"
            },
            "requestId": "6e8356f9-489b-4c7b-8ba6-c8cd74f25455",
            "requestTime": "13/Jul/2022:11:58:59 +0000",
            "requestTimeEpoch": 1657713539
        },
        "url": ""
    }
}